2. Micro-Electro-Mechanical Systems (MEMS)
Abstract:
MEMS technology consists of microelectronic elements, actuators, sensors, and mechanical structures
built onto a substrate, which is usually silicon. They are developed using microfabrication techniques:
deposition, patterning, and etching. The most common forms of production for MEMS are bulk
micromachining, surface micromachining, and HAR fabrication. The benefits on this small scale
integration brings the technology to a vast number and variety of devices.
Used for sensing, actuation or are passive micro-structures.
Usually integrated with electronic circuitry for control
and/or information processing.
3. - What Are MEMS?
- Components of MEMS
- Fabrication
- MEMS Operation
- Applications
- Summary
Introduction
4. What are MEMS?
MEMS technology consists of microelectronic elements, actuators, sensors, and mechanical
structures built onto a substrate, which is usually silicon.
5. MEMS
• Made up of components between 1-100 micrometers in size
• Devices vary from below one micron up to several mm
• Functional elements of MEMS are miniaturized structures, sensors,
actuators, and microelectronics
• One main criterion of MEMS is that there are at least some elements
that have mechanical functionality, whether or not they can move
6. Components
Microelectronics:
• “brain” that receives, processes, and makes decisions
• data comes from microsensors
Microsensors:
• constantly gather data from environment
• pass data to microelectronics for processing
• can monitor mechanical, thermal, biological, chemical
readings
Microactuator:
• acts as trigger to activate external device
• microelectronics will tell microactuator to activate device
Microstructures:
• extremely small structures built onto surface of chip
• built right into silicon of MEMS
8. Fabrication Processes
Deposition:
• deposit thin film of material (mask) anywhere between a few nm to 100 micrometers onto
substrate
• physical: material placed onto substrate, techniques include sputtering and evaporation
• chemical: stream of source gas reacts on substrate to grow product, techniques include
chemical vapor deposition and atomic layer deposition
• substrates: silicon, glass, quartz
• thin films:polysilicon, silicon
dioxide, silicon nitride, metals,
polymers
9. Patterning:
• transfer of a pattern into a material
after deposition in order to prepare for etching
• techniques include some type of lithography,
photolithography is common
Etching:
• wet etching: dipping substrate into chemical
solution that selectively removes material
• process provides good selectivity, etching rate
of target material higher that mask material
• dry etching: material sputtered or dissolved
from substrate with plasma or gas variations
• choosing a method: desired shapes, etch depth and uniformity, surface roughness, process
compatibility, safety, cost, availability, environmental impact
10. Summary: MEMS fabrication
MEMS technology is based on silicon microelectronics
technology
Main MEMS techniques :
Bulk micromachining
Surface micromachining
LIGA and variations
Wafer bonding
11. Summary: MEMS fabrication
Bulk Micromachining:
• oldest micromachining technology
• technique involves selective removal of substrate to produce mechanical
components
• accomplished by physical or chemical process with chemical being used
more for MEMS production
• chemical wet etching is popular because of high etch rate and selectivity
• isotropic wet etching: etch rate not dependent on crystallographic
orientation of substrate and etching moves at equal rates in all directions
• anisotropic wet etching: etch rate is dependent on crystallographic
orientation of substrate
12. Surface Micromachining:
• process starts with deposition of thin-film that acts as a temporary
mechanical layer (sacrificial layer)
• device layers are constructed on top
• deposition and patterning of structural layer
• removal of temporary layer to allow movement of structural layer
• benefits: variety of structure, sacrificial and etchant combinations, uses
single-sided wafer processing
• allows higher integration density and lower resultant per die cost
compared to bulk micromachining
• disadvantages: mechanical properties of most thin-films are usually
unknown and reproducibility of their mechanical properties
14. Wafer Bonding:
• Method that involves joining two or more
wafers together to create a wafer stack
• Three types of wafer bonding: direct bonding,
anodic bonding, and intermediate layer bonding
• All require substrates that are flat, smooth,
and clean in order to be efficient and successful
High Aspect Ratio Fabrication (Silicon):
• Deep reactive ion etching (DRIE)
• Enables very high aspect ratio etches to be
performed into silicon substrates
• Sidewalls of the etched holes are nearly vertical
• Depth of the etch can be hundreds
or even thousands of microns into the silicon substrate.
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17. Applications: Sensors
Acceleration :
Air bag crash sensing
Seat belt tension
Automobile suspension control
Human activity for pacemaker control
Vibration :
Engine management
Security devices
Monitoring of seismic activity
Angle of inclination
Vehicle stability and roll
25. Optical MEMS
Ex: optical switches, digital micromirror
devices (DMD), bistable mirrors, laser
scanners, optical shutters, and dynamic
micromirror displays
RF MEMS
Smaller, cheaper, better way to
manipulate RF signals
Reliability is issue, but getting there
Additional Applications
26. Some future applications
Biological applications:
Microfluidics
Lab-on-a-Chip
Micropumps
Resonant microbalances
Micro Total Analysis systems
Mobile communications:
Micromechanical resonator for resonant circuits
and filters
Optical communications:
Optical switching
27. Much smaller area
Cheaper than alternatives
In medical market, that means
disposable
Can be integrated with electronics (system
on one chip)
Speed:
Lower thermal time constant
Rapid response times(high frequency)
Power consumption:
low actuation energy
low heating power
Benefits Disadvantages
Imperfect fabrication
techniques
Difficult to design on micro
scales
28. Summary/Conclusion
Micro-Electro-Mechanical Systems are 1-100 micrometer
devices that convert electrical energy to mechanical
energy and vice-versa.
The three basic steps to MEMS fabrication are deposition,
patterning, and etching.
Due to their small size, they can exhibit certain
characteristics that their macro equivalents can’t. MEMS
produce benefits in speed, complexity, power
consumption, device area, and system integration. These
benefits make MEMS a great choice for devices in
numerous fields.
Notas do Editor
The precise dispensing of small amounts of liquids (amounts as
minute as a picoliter and flow rates of as low as a few
microliters per minute) found in needleless injectors,
nebulizers, insulin pumps, and drug delivery systems.
Sub-dermal glucose monitors that not only monitor one's
glucose levels, but also deliver the necessary amount of insulin.
The picture to the right of the MiniMed Paradigm 522 shows a
diabetic patient wearing a chemical sensor (C) that measures
the blood glucose and a transmitter (D) that sends the
measurement to the a computer in (A). (A) also contains a
micropump that delivers a precise amount of insulin
through the cannula (B) to the patient. This is a
continuous bioMEMS monitoring and drug delivery
system that has eliminated the traditional finger
pricks for blood samples that diabetics have to do
daily.
MEMS tweezers or miniature robot arms that move, rotate, cut and place molecules, sort cells
and proteins, and manipulate organelles and DNA inside a living cell.5
Miniature surgical tools that incorporate sensing and measuring devices.
Medical diagnostics (glucose monitoring, blood analysis, cells counts and numerous others).
Biosensing devices used to measure biomolecular information
(cells, antibodies, DNA, RNA enzymes)
Medical stents inserted into previously blocked arteries to open
and maintain a clear channel for blood flow (see Stent Delivery
Catheter to right). There devices are coated with a nanocoating
of a drug that is slowly released into the bloodstream over time.
This prevents a re-narrowing of the artery and future
procedures.
DNA microarrays used to test for genetic diseases, medicine
interaction, and other biological markers.
DNA duplication devices such as the Polymerase Chain
Reaction (PCR) system that takes a miniscule bit of DNA,
amplifies it and produces an exact duplication.
The precise dispensing of small amounts of liquids (amounts as
minute as a picoliter and flow rates of as low as a few
microliters per minute) found in needleless injectors,
nebulizers, insulin pumps, and drug delivery systems.
Sub-dermal glucose monitors that not only monitor one's
glucose levels, but also deliver the necessary amount of insulin.
The picture to the right of the MiniMed Paradigm 522 shows a
diabetic patient wearing a chemical sensor (C) that measures
the blood glucose and a transmitter (D) that sends the
measurement to the a computer in (A). (A) also contains a
micropump that delivers a precise amount of insulin
through the cannula (B) to the patient. This is a
continuous bioMEMS monitoring and drug delivery
system that has eliminated the traditional finger
pricks for blood samples that diabetics have to do
daily.
MEMS tweezers or miniature robot arms that move, rotate, cut and place molecules, sort cells
and proteins, and manipulate organelles and DNA inside a living cell.5
Miniature surgical tools that incorporate sensing and measuring devices.
Medical diagnostics (glucose monitoring, blood analysis, cells counts and numerous others).
Biosensing devices used to measure biomolecular information
(cells, antibodies, DNA, RNA enzymes)
Medical stents inserted into previously blocked arteries to open
and maintain a clear channel for blood flow (see Stent Delivery
Catheter to right). There devices are coated with a nanocoating
of a drug that is slowly released into the bloodstream over time.
This prevents a re-narrowing of the artery and future
procedures.
DNA microarrays used to test for genetic diseases, medicine
interaction, and other biological markers.
DNA duplication devices such as the Polymerase Chain
Reaction (PCR) system that takes a miniscule bit of DNA,
amplifies it and produces an exact duplication.
The precise dispensing of small amounts of liquids (amounts as
minute as a picoliter and flow rates of as low as a few
microliters per minute) found in needleless injectors,
nebulizers, insulin pumps, and drug delivery systems.
Sub-dermal glucose monitors that not only monitor one's
glucose levels, but also deliver the necessary amount of insulin.
The picture to the right of the MiniMed Paradigm 522 shows a
diabetic patient wearing a chemical sensor (C) that measures
the blood glucose and a transmitter (D) that sends the
measurement to the a computer in (A). (A) also contains a
micropump that delivers a precise amount of insulin
through the cannula (B) to the patient. This is a
continuous bioMEMS monitoring and drug delivery
system that has eliminated the traditional finger
pricks for blood samples that diabetics have to do
daily.
MEMS tweezers or miniature robot arms that move, rotate, cut and place molecules, sort cells
and proteins, and manipulate organelles and DNA inside a living cell.5
Miniature surgical tools that incorporate sensing and measuring devices.
Medical diagnostics (glucose monitoring, blood analysis, cells counts and numerous others).
Biosensing devices used to measure biomolecular information
(cells, antibodies, DNA, RNA enzymes)
Medical stents inserted into previously blocked arteries to open
and maintain a clear channel for blood flow (see Stent Delivery
Catheter to right). There devices are coated with a nanocoating
of a drug that is slowly released into the bloodstream over time.
This prevents a re-narrowing of the artery and future
procedures.
DNA microarrays used to test for genetic diseases, medicine
interaction, and other biological markers.
DNA duplication devices such as the Polymerase Chain
Reaction (PCR) system that takes a miniscule bit of DNA,
amplifies it and produces an exact duplication.